[postgis-users] different results for area with different programms

[Martin Davis]

I wonder about the PostGIS value, too. JTS gives 9.336164500133789.

On 2/23/2012 6:58 AM, Astrid Emde wrote:
> Hello,
>
> I calculate the area of polygons and get different results with diffrent
> programms.
>
> Here is an example polygon:
>
> Select st_area(geometryfromtext(
> 'POLYGON ((
>    2569220.83 5630370.607,
>    2569215.357 5630374.968,
>    2569216.017 5630375.795,
>    2569216.19 5630376.01,
>    2569221.663 5630371.649,
>    2569220.83 5630370.607
> ))',31466) );
>
> These are the results that I get:
> * PostGIS: 9.337890625 (with "POSTGIS="1.5.1" GEOS="3.2.0-CAPI-1.6.0")
>
> * AutoCAD Map 2012: 9.3362
> * Kanal++ [1]: 9.3361645
>
> PostGIS gives back a slightly bigger area than the other programms. Do you
>
> know why and who is right?
>
> Best regards
>
> Astrid
>
> [1]
> http://tandler.com/communal_gis/watermanagment/wastewater/sewer-gis-kanalplusplus.htm
>